This invention relates to methods of immunizing against Helicobacter infection.
Cholera toxin (CT) and the heat-labile-enterotoxin of E. coli (LT) are commonly used as immunological adjuvants for mucosal immunization. The non-toxic B subunit of LT (LTB) has also been shown to have mucosal immunomodulating activity. When delivered mucosally with urease or other Helicobacter antigens, LT and CT each induce immune responses that protect mice against infection with Helicobacter pylori. 
Xu-Amano et al. (J. Exp. Med. 178:1309-1320, 1993) showed that mice develop specific serum IgM and IgG (but not IgA) responses following intraperitoneal immunization with tetanus toxin (TT) plus CT. TT alone gave low responses. Hornquist, et al. (Eur. J. Immunol. 23:2136-2143, 1993) showed that CT promotes priming of CD4+ T cells when delivered intravenously with Keyhole Limpet Hemocyanin (KLH). Marinaro et al. (J. Immunol. 155:4621-4629, 1995) showed that CT stimulates production of serum IgE to TT when the antigen and adjuvant are delivered subcutaneously.
We have discovered that parenterally delivered LT and LTB are effective adjuvants that enhance the immunoprotective effect of Helicobacter antigens, such as urease. We have also discovered that LT+LTB gives better results that LT alone.
Accordingly, the invention provides methods of inducing a protective or therapeutic immune response to Helicobacter infection in a mammal, in which (a) a Helicobacter antigen, and (b) an adjuvant including one or more of (i) LT, (ii) LTB, (iii) CT, and (iv) CTB (e.g., LT+LTB) is parenterally (e.g., subcutaneously, intradermally, intramuscularly, or intravenously) administered to a mammal.
The antigen and the adjuvant can be provided together in a solution, or separately. The antigen can be urease or a subunit, enzymatically inactivate derivative, or fragment thereof. The antigen can also be catalase, HspA, HspB, lactoferrin receptor, p76 (SEQ ID NOs:1-22), p32 (SEQ ID NOs:23 and 24), BabA, BabB, AlpA, AlpB, or an immunogenic fragment or derivative thereof. The methods of the invention also include the administration of more than one Helicobacter antigen.
The invention provides several advantages. For example, parenteral delivery of LT is advantageous in that the toxin does not contact the intestinal epithelial cells, and thus does not cause diarrhea. Also, the toxicity of parenterally administered LT we observed was limited to injection site swelling, and we observed no toxicity with LTB at high doses (see below), which matched the effectiveness of LT in augmenting protective immunity. Also, our observation of the heightened effect of parenterally administering LT (low dose)+LTB (high dose) minimizes the possibility of any potential side effects.
Other features and advantages of the invention are apparent from the following detailed description, the drawings, and the claims.